Diagnostic ultrasound ( PDFDrive )

266 PART II Abdominal and Pelvic Sonography
cell type or, more oten, as primary lymphoma of the GI tract,
which is virtually always a non-Hodgkin lymphoma. Primary
tumors constitute only 2% to 4% of all GI tract malignant tumors 12
but account for 20% of those found in the small bowel. hree
predominant growth patterns are observed: nodular or polypoid,
carcinoma-like ulcerations, and iniltrating tumor masses that
frequently invade the adjacent mesentery and lymph nodes.
Small, submucosal nodules may be easily overlooked on
sonography. However, many patients have large, easily visible,
very hypoechoic, ulcerated masses in the stomach or small
bowel 14,15 (Fig. 8.10). Long, linear, high-amplitude echoes with
ring-down artifacts, indicating gas in the residual lumen or
ulcerations, and aneurysmal dilation of the bowel lumen are
common observations. his particular pathologic state has been
recognized as one of the more frequent presentations of patients
with acquired immunodeiciency syndrome (AIDS)–related
lymphoma. Regional lymph node enlargement may be visualized,
although generalized lymph node abnormality is uncommon.
Metastases
Malignant melanoma and primary tumors of the lung and breast
are the tumors most likely to have secondary involvement of the
GI tract 16 (Fig. 8.11). In order of frequency, the stomach, small
bowel, and colon are involved. On sonography, small submucosal
nodules that tend to ulcerate are rarely seen, whereas large,
difusely iniltrative tumors with large ulcerations are common,
particularly in the small bowel where they create hypoechoic,
well-deined masses that oten have bright, specular echoes with
ring-down artifacts in areas of ulceration.
Secondary neoplasm afecting the omentum and peritoneum
may cause ascites (which may be particulate ascites), tiny or
conluent supericial secondary nodules on the gut surface, or
extensive omental cakes that virtually engulf the involved gut
loops 17 (Fig. 8.12). Metastases to the peritoneum most oten
arise from primary tumors in the ovary or the gut. A drop
metastasis in the pelvic pouch of Douglas shows as a small,
solid, peritoneal nodule without obvious origin from the pelvic
viscera.
INFLAMMATORY BOWEL DISEASE:
CROHN DISEASE
Inlammatory bowel disease (IBD) comprises Crohn disease and
ulcerative colitis. Ulcerative colitis is a mucosal inlammation
of the colon and oten shows little in the way of gross morphologic
A
B
C
D
FIG. 8.10 Small Bowel Lymphoma in Two Patients. (A) Transverse left sonogram shows a hypoechoic round mass lesion. Central echogenicity
with ring-down gas artifact suggests its gut origin. (B) Correlative CT scan shows large, soft tissue mass with corresponding residual gut lumen.
(C) Sonogram in AIDs patient shows a focal midabdominal, hypoechoic mass with no wall layer deinition, which is classic for gut lymphoma. The
luminal gas appears as central bright echogenicity with dirty shadowing. (D) Correlative CT scan.